This study is aimed at evaluating the potential that chronic wasting disease, a prion disease of deer or elk, might be transmissible to humans. This concern is amplified by the finding that humans appear to be susceptible to infection by a cattle prion disease, bovine spongiform encephalopathy (mad cow disase). To study the possibility of cross-species transmission of CWD, two species of nonhuman primates, squirrel monkeys and cynomologus macaques, were infected orally or intracerebrally with brain material derived from CWD affected deer or elk. Three years after infection intracerebrally infected squirrel monkeys developed clinical neurological signs and were confirmed by biochemical and pathological testing of brain to have a prion disease. Observations on the remaining monkeys will continue for at least a few more years